An interesting study was performed in six anesthetized mechanically ventilated piglets weighting 30 kg. The viscoelastic properties of lungs and thoracic wall were investigated and serve as a viscoelastic model.

Animals were tracheotomized, anesthetized and mechanically ventilated under controlled conditions.

After control measurements of the mechanical properties of the lung of the pigs had been taken, acute lung injury (ALI) was induced by saline lavage. Lung and thoracic wall tissue resistance (¬¶¬§R), which reflects viscoelastic properties and/or time constant inequalities, were determined by using a rapid airway occlusion technique during constant flow inflation ( ), at constant tidal volume. was varied from 0.1¬®C0.2 to 1.2 L second1 on a single breath.

Multiple data sets of ¬¶¬§R of lung (¬¶¬§RL) and thoracic wall (¬¶¬§Rw) to inspiratory time (TI = VT/ ) were fitted to a model whose prediction equation was ¬¶¬§R = R2[1 −exp(−TI/¬¶√ď2)], where R2 and ¬¶√ď2 are the ¬°¬ģviscoelastic¬°¬Į resistance and time constant, respectively.

The corresponding values of ¬¶√ď2,L were 7.1 (5.1¬®C11.6) and 4.4 (3.1¬®C5.5) seconds. The values pertaining to thoracic wall did not change significantly among conditions.

Conclusions and clinical relevance: Viscoelastic properties of the lung and thoracic wall in piglets can be described by a viscoelastic model. Values of parameters of this model were markedly increased in ALI and decreased with PEEP.

Pasteurella multocida diversity in poultry and pigs in Australia
This recently published study investigates the genotype and diversity of Pasteurella multocida present in pig herds and determines the extent of overlap with isolates from poultry flocks in Australia. Do the isolates vary? A very interesting study not only for Australia.